100 prisoners: Difference between revisions
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0 % success for random
32.9 % success for optimal strategy
</pre>
=={{header|Vlang}}==
{{trans|Wren}}
<lang vlang>import rand
import rand.seed
// Uses 0-based numbering rather than 1-based numbering throughout.
fn do_trials(trials int, np int, strategy string) {
mut pardoned := 0
for _ in 0..trials {
mut drawers := []int{len: 100, init: it}
rand.shuffle<int>(mut drawers) or {panic('shuffle failed')}
mut next_trial := false
for p in 0..np {
mut next_prisoner := false
if strategy == "optimal" {
mut prev := p
for _ in 0..50 {
this := drawers[prev]
if this == p {
next_prisoner = true
break
}
prev = this
}
} else {
// Assumes a prisoner remembers previous drawers (s)he opened
// and chooses at random from the others.
mut opened := [100]bool{}
for _ in 0..50 {
mut n := 0
for {
n = rand.intn(100) or {0}
if !opened[n] {
opened[n] = true
break
}
}
if drawers[n] == p {
next_prisoner = true
break
}
}
}
if !next_prisoner {
next_trial = true
break
}
}
if !next_trial {
pardoned++
}
}
rf := f64(pardoned) / f64(trials) * 100
println(" strategy = ${strategy:-7} pardoned = ${pardoned:-6} relative frequency = ${rf:-5.2f}%\n")
}
fn main() {
rand.seed(seed.time_seed_array(2))
trials := 100000
for np in [10, 100] {
println("Results from $trials trials with $np prisoners:\n")
for strategy in ["random", "optimal"] {
do_trials(trials, np, strategy)
}
}
}</lang>
{{out}}
Sample run:
<pre>
Results from 100000 trials with 10 prisoners:
strategy = random pardoned = 91 relative frequency = 0.09 %
strategy = optimal pardoned = 31321 relative frequency = 31.32%
Results from 100000 trials with 100 prisoners:
strategy = random pardoned = 0 relative frequency = 0.00 %
strategy = optimal pardoned = 31318 relative frequency = 31.32%
</pre>
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